Video mixers are well known in the broadcast industry in both studio and outside broadcast environments and are used to synthesise a variety of program sources to generate program material. The program sources may be, for example: program material from different camera angles, for example at a football match or in a studio; clips from a clip store; or pre-recorded video material.
There are a number of different ways of combining the program sources to form the output program material. At the simplest, the output program material might be cut from one source, for example a live camera in a news studio, to second source, for example pre-recorded video material from an archive, which is relevant to current news story. In more complicated situations a fade or a wipe may be used to make a transition from one program source to another program source. In addition, a key source may be used to “cut through” a first program source and a second source may be inserted into the hole cut by the key. This technique allows effects such as displays of logos or sports match score boards, or picture-in-picture effects, to be achieved.
Therefore it can be seen that for many of the functions a video mixer is required to perform, the video mixer must combine picture information from more than one source to generate the output program material.
Established digital television standards are collectively termed Standard Definition (SD) television standards and currently a number of High Definition (HD) television standards have been developed. A major difference between SD and HD programming is that each HD picture has a far greater number of pixels, resulting in a higher data rate for processing.
Increasingly it is to be expected that a video mixer will be required to accept HD and SD program material as program sources and to produce both HD and SD program material.